1. Field of the Invention
The present invention relates to a fluorine-containing copolymer composition, and more particularly to a fluorine-containing copolymer composition comprising a fluorine-containing elastomer and a fluororesin.
2. Related Art
Fluorine-containing elastomers are distinguished in heat resistance, oil resistance, chemical resistance, etc. and their vulcanization molding products are widely used as various seal materials such as oil seals, O-rings, packings, gaskets, etc. However, further improvement is still desired in the following points in spite of even such distinguished characteristics of fluorine-containing elastomers.
(1) Roll Processability:
Generally, most of the fluorine-containing elastomers are not on a satisfactory level with respect to roll processability (windability) and moldability. To solve the problem, JP-B-2-40694 proposes to add a fluorine-containing thermoplastic elastomer to the fluorine-containing elastomer. Nearly satisfactory improvement effect can be obtained thereby. In JP-B-2-40694, the fluorine-containing elastomer and the fluorine-containing thermoplastic elastomer are used in a ratio by weight of the former to the latter of 30:70 (Example 1), 50:50 (Example 2) and 80:20 (Comparative Example 2), and thus the proposed composition can be regarded as a fluorine rubber composition comprising the fluorine-containing thermoplastic elastomer as the major component.
The fluorine-containing thermoplastic elastomer for that purpose is produced by multi-block polymerization (JP-A-53-3495 and JP-B-61-49327), and thus entails a problem of high production cost. The composition range of the disclosed multiblock polymers inevitably gives rise to higher hardness of the crosslinking molding products (in these specification no mention is made of the hardness), limitation of the mixing proportion of a reinforcing filler, etc., thereby restricting the degree of freedom of blend design.
(2) Mechanical Strength:
Generally, the fluorine-containing elastomer has a substantially satisfactory tensile strength (usually strength at break), but its 100% modulus as a strength in the practical service surrounding is not always satisfactory.